Golf club head

ABSTRACT

An iron-type golf club head has a face having a face surface of a flat surface, and a hosel which is continuous with the face on its heel side. A shaft insertion hole is disposed in the hosel. A protrusion protruding rearward in the vicinity of the center in a toe-heel direction is disposed. A material of the golf club head is pure iron having a high purity of at least 99.995%, for instance, a purity within a range of 99.995 to 99.9999%. The golf club head is subjected to carburizing so that carbon diffuses to a range of about 0.2 to 0.5 mm from the surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf club head, particularly to a golf club head whose face is made of an iron material. More specifically, the invention relates to a golf club head for use in an iron-type golf club.

2. Description of the Related Art

As a material for an iron-type golf club head, a soft iron, stainless steel, a cupper alloy, and the like, has been used. In addition, an iron golf club head of a composite type whose peripheral edge section is made of stainless steel, and to which a face plate made of a titanium alloy is attached has come into widespread use in recent years. Hereinbelow, an iron-type golf club head is often referred to as an “iron head.”

An iron head made of pure iron whose purity falls within a range of 99.93 to 99.97% is disclosed in JP-A-63-229078. In lines 1 to 8, upper left column, page 3 of the specification, it is disclosed that pure iron has great elongation and drawing ratio, and is superior in malleability, accordingly, a contact area between a golf ball and a face of the iron head made of pure iron is expanded, and a contact time is elongated, thereby enhancing directional stability of a hit ball.

Forming a surface hardening layer on an iron head made of a soft iron material by means of carburizing or nitriding is disclosed in JP-A-8-206260.

Application of plasma carburizing or gas carburizing to an iron head made of a structural alloy steel, stainless steel, titanium, or a titanium alloy steel so as to increase surface hardness, thereby enhancing a carry distance of a hit ball is disclosed in JP-A-10-5376 (paragraphs [0008] to [0017]).

As compared with an iron head made of stainless steel, an iron head made of pure iron is lower in material hardness and produces a softer ball-hit feeling. However, because of low abrasive resistance, the iron head made of pure iron is easily damaged on its surface, and angular edges of score lines (lateral grooves on a face surface) are rounded at an early stage, thereby making it difficult to impart spin to a hit ball.

Increasing surface hardness of an iron head made of a soft iron material or an alloy steel by means of carburizing is disclosed in the above-mentioned JP-A-8-206260 and JP-A-10-5376, however, application of carburizing to an iron head made of a pure iron material is not described therein.

SUMMARY OF THE INVENTION

The present invention provides a golf club head which is superior in ball-hit feeling as well as in abrasive resistance.

According to aspect 1 of the invention, a golf club head includes a face made of an iron material which is carburized, and is characterized in that the iron material is pure iron.

The invention of aspect 2 is the golf club head characterized in that in the golf club head of aspect 1, purity of the pure iron is at least 99.8%.

The invention of aspect 3 is the golf club head characterized in that in the golf club head of aspect 1, the golf club head is an iron-type golf club head.

The invention of aspect 4 is the golf club head characterized in that in the golf club head of aspect 3, the iron-type golf club head has a loft angle of 25° or more.

The invention of aspect 5 is the golf club head characterized in that in the golf club head of aspect 3, a thickness of the face in a vicinity of a center of gravity thereof falls within a range of 3.5 to 15 mm.

The invention of aspect 6 is the golf club head characterized in that in the golf club head of aspect 5, the face is of smaller thickness on a toe side and on a heel side than in the vicinity of its center of gravity of the face.

The invention of aspect 7 is the golf club head characterized in that in the golf club head of aspect 1, hardness of a surface of the face falls within a range of HV (hardness value of Vickers) 180 to 900.

In particular, since surface hardness of stainless steel (SUS630)—which is generally regarded to be resistant to damage when used as an iron head—is about HV 300, hardness of the face surface is preferably greater than or equal to HV 300.

Being made of a pure iron material, the golf club head of the invention provides softball-hit feeling. Accordingly, the golf club head is particularly suitable for use in an iron having a loft angle greater than or equal to 25° and from which a soft touch upon hitting of a ball is expected, and further particularly suitable for use in a wedge whose loft angle falls within a range of 400 to 650.

According to the invention, when purity of an iron material is greater than or equal to 99.8%, ball-hit feeling becomes soft. Accordingly, carbon content is preferably 0.02% or lower. When an iron material having a high purity of 99.995% or higher is employed, ball-hit feeling becomes fairly soft, and stainless property is also improved, which is advantageous.

According to the invention, a surface of a head made of the pure iron is subjected to carburizing. Accordingly, the head exhibits favorable abrasive resistance.

The golf club head according to the invention is suitable for application to an iron head as described above, however, being made of pure iron, the face may have insufficient strength. To this end, the face in the vicinity of a center of gravity at which a ball hits is preferably reinforced so as to be 3.5 to 15 mm in thickness. In addition, when thickness of the face in the vicinity of the center of gravity is increased, a fairly favorable tactile response is obtained when a ball is hit in the vicinity of the center of gravity (a so-called hitting of the ball center with the gravity center of a head).

Meanwhile, in order to suppress an increase in weight of the iron head, the following is preferable, that is, thickness in the vicinity of the center of gravity of the face is increased while thicknesses of the remaining portions are rendered smaller. More specifically, the face is preferably smaller in thickness on its toe side and on its heel side than in the vicinity of its center of gravity.

According to the invention, carburizing is preferably applied so that surface hardness of the face falls within a range of about HV 180 to 900.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an iron-type golf club head according to an embodiment of the invention, as viewed from the rear; and

FIG. 2 is a side view of the iron-type golf club head according to the embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the invention will be described further in detail by reference to the drawings. FIG. 1 is a perspective view of a golf club head according to an embodiment of the invention, as viewed from the rear. FIG. 2 is a side view of the same as viewed from the toe side thereof.

An iron-type golf club head 1 has a face 2 which has a face surface 2 f of a flat shape, and a hosel 3 which is continuous with the face 2 on its heel side. A shaft insertion hole 4 is disposed in the hosel 3. A tip of a golf club shaft is inserted into the shaft insertion hole 4, and fixedly attached thereto by means of an adhesive.

The golf club head 1 shown in the drawings is a wedge whose loft angle is 45°. On the backside of the golf club head 1, a protrusion 5 protruding rearward in the vicinity of the center in a toe-heel direction is disposed. The face 2 is substantially uniform in thickness, except for the protrusion 5.

Meanwhile, the face 2 has its greatest thickness at a sole 6 side (bottom section side), and thickness is gradually reduced upward.

The protrusion 5 is located rearward of the center of gravity of the face 2 (i.e., rearward in a state where the sole of the head 1 is in contact with the ground).

The protrusion 5 is preferably located within a range of about 10 to 90%, particularly preferably about 20 to 80%, in terms of a ratio of a total length of the head 1 in the toe-heel direction and a distance from the protrusion 5 to the farther of the toe and the heel.

A lowest portion of the protrusion 5 desirably reaches the sole 6. Accordingly, the center of gravity of the head 1 can be lowered. In addition, in the embodiment, the outer surface of the protrusion 5 is rendered smoothly continuous with the sole 6 as shown in FIG. 2. When configured as above, the lower portion of the protrusion 5 can be utilized as a bounce angle of the head 1.

A material of the golf club head 1 is pure iron having a high purity of at least 99.995%, for instance, within a range of 99.995 to 99.9999%. The head 1 is subjected to carburizing so that carbon diffuses to a range of about 0.2 to 0.5 mm from the surface. The carburizing may be applied either only onto the face surface 2 f or onto the whole head. The carburizing may be either gas carburizing or plasma carburizing.

As a result of the carburizing, surface hardness of the head 1 is preferably rendered HV 180 to 900, particularly preferably HV 300 to 900, further preferably HV 300 to 800.

By virtue of being made of pure iron of high purity, the golf club head 1 configured as above provides soft ball-hit feeling and is superior in stainless property. Furthermore, by virtue of being carburized, the golf club head 1 is superior in abrasive resistance.

A surface of a soft iron material, such as S20C, which is generally employed for an iron head, is hardened by means of carburizing, however, when the carburized portion is lost as a result of damage or the like, rust is formed. However, when pure iron of high purity is employed, by means of carburizing the entire head, the shape of the head is maintained, and rust is hardly formed even when damage extends to a great depth.

The golf club head 1 is provided with the protrusion 5. Accordingly, the face 2 is high in strength, and the golf club head 1 is fairly superior in tactile response when a ball is hit in the vicinity of the center of gravity of the face. In addition, the golf club head 1 has the center of gravity at a deep position, and therefore a wide sweet area.

Of the golf club head 1, the protrusion 5 reaches the sole 6. Accordingly, the center of gravity is at a low position, thereby facilitating hitting a ball high.

The golf club head of the invention is suitable for an iron head whose loft angle is greater than or equal to 25°, particularly suitable for a wedge-type head whose loft angle is greater than or equal to 40°. However, the golf club head is also applicable to a head of a fairway wood club or utility club made of an iron material.

A member of a material of high specific gravity, such as tungsten, may be attached onto the sole of the golf club head of the invention. In addition, a hollow may be disposed inside the face, and filled with a vibration absorption material such as rubber or elastomer. 

1. A golf club head comprising: a face made of a iron material which is carburized, wherein the iron material is pure iron.
 2. The golf club head according to claim 1, wherein purity of the pure iron is at least 99.8%.
 3. The golf club head according to claim 1, wherein the golf club head is an iron-type golf club head.
 4. The golf club head according to claim 2, wherein the golf club head is an iron-type golf club head.
 5. The golf club head according to claim 3, wherein the iron-type golf club head has a loft angle of 25° or more.
 6. The golf club head according to claim 4, wherein the iron-type golf club head has a loft angle of 25° or more.
 7. The golf club head according to claim 3, wherein a thickness of the face in a vicinity of a center of gravity of the face falls within a range of 3.5 to 15 mm.
 8. The golf club head according to claim 5, wherein a thickness of the face in a vicinity of a center of gravity of the face falls within a range of 3.5 to 15 mm.
 9. The golf club head according to claim 7, wherein the face is of smaller thickness on a toe side and on a heel side than in the vicinity of the center of gravity of the face.
 10. The golf club head according to claim 8, wherein the face is of smaller thickness on a toe side and on a heel side than in the vicinity of the center of gravity of the face.
 11. The golf club head according to claim 1, wherein hardness of a surface of the face falls within a range of HV 180 to
 900. 